Struct Topic 

pub struct Topic<T> { /* private fields */ }

A channel that accumulates all written values.

Unlike LastValue which keeps only the most recent value, Topic appends all writes to a list. This is useful for collecting multiple results or building up a history.

Example

use rust_langgraph::channels::{BaseChannel, Topic};

let mut channel = Topic::<String>::new();
channel.update(vec![serde_json::json!("first")]).unwrap();
channel.update(vec![serde_json::json!("second")]).unwrap();

let values: Vec<String> = serde_json::from_value(
    channel.get().unwrap().unwrap()
).unwrap();
assert_eq!(values, vec!["first", "second"]);

Implementations

impl<T> Topic<T>

pub fn new() -> Self

Create a new empty Topic channel

pub fn with_values(values: Vec<T>) -> Self

Create a Topic with initial values

pub fn len(&self) -> usize

Get the number of accumulated values

pub fn is_empty(&self) -> bool

Check if the topic is empty

Trait Implementations

impl<T> BaseChannel for Topic<T>

where T: Serialize + for<'de> Deserialize<'de> + Clone + Send + Sync + Debug + 'static,

fn get(&self) -> Result<Option<Value>>

Get the current value as JSON

fn update(&mut self, values: Vec<Value>) -> Result<()>

Update the channel with new values

fn checkpoint(&self) -> Result<Value>

Serialize the channel state for checkpointing

fn from_checkpoint(data: Value) -> Result<Box<dyn BaseChannel>>

Restore the channel state from a checkpoint

fn type_name(&self) -> &'static str

Get the channel’s type name for debugging

fn is_empty(&self) -> bool

Check if the channel is empty

impl<T: Clone> Clone for Topic<T>

fn clone(&self) -> Topic<T>

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl<T: Debug> Debug for Topic<T>

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl<T> Default for Topic<T>

fn default() -> Self

Returns the “default value” for a type.